The vulnerability (CVE-2026-45945) in the Linux kernel concerns a race condition during replacement of Intel VT-d PASID table entries. The PASID entry is 512 bits, but hardware reads it in 128-bit chunks. The prior implementation replaced the entire entry atomically via structure assignment while the entry was active (Present bit set), risking torn reads where hardware could see a mix of old and new data. This inconsistent state could cause unpredictable IOMMU behavior or spurious faults. The fix removes unsafe replacement helpers and enforces a clear-then-update sequence that clears the Present bit and completes invalidation before applying the new entry, preventing torn reads.

If exploited, this race condition could cause the IOMMU hardware to observe inconsistent PASID entry states, potentially leading to unpredictable behavior or spurious faults affecting system stability and security. The CVSS vector indicates local attack complexity, low privileges required, and high impact on confidentiality, integrity, and availability.

A fix is available and has been applied in the Linux kernel to address this race condition by changing the PASID entry update method to clear-then-update. Users should apply the official Linux kernel updates that include this fix. Patch status is not explicitly stated here; check the Linux kernel vendor advisory for the exact fixed versions and update guidance.